Suppression of shock and vibration in a sports racket has been a critical design goal that has eluded experts in the field. The prior art is very extensive in descriptions of arrangements designed to reduce vibration in a racket frame by means of using foam material, composite material, in sandwich form or in homogeneous types, by means of vibration dampers near the top of the frame or near the throat either in separate attachments or as an integral part of the frame, attached on strings or on frames, etc. In these arrangements employing vibration dampers attached on strings, most are installed locally near the throat or the head which can affect only a few nearby strings. However, since disturbance caused by the impact of a ball spreads far and wide in the whole string network, damping of a few strings cannot be very effective.
In the prior art, U.S. Pat. No. 4,322,076 to Bertram et al discloses longitudinal strings which are bent, except for the through which the strings extend and against which they slide. The specification does not suggest the additional purpose of damping, on the contrary, the function encountered in the racket throat from the sliding of the bent strings in the face 2 would render such damping ineffective.
Similarly, in U.S. Pat. Nos. 1,663,039, 1,790,156, 2,165,701, 2,206,548 and 4,099,717 disclose arrangements wherein passing strings are bent along the way to an anchoring means which are utilized for mechanically adjusting the longitudinal strings at or near their respective handles. Vibration damping the collected strings at a single anchoring point was never intended by the patentees, nor could their design arrangements adapt to such a possibility.
The present invention was devised to overcome the problems discussed above and considers that the longitudinal string group, which transmits the major portion of the shock load to the hand, may be channeled toward the handle in a converging manner such that a localized shock absorbing devise, installed at the converging point of these strings, may damp a large number of the longitudinal strings effectively to achieve the purpose of shock absorbing of the frame to a degree that was not possible before. The success of this arrangement depends upon two aspects of the design: 1) a large number of the longitudinal strings should be led toward that localized damping device; 2) the damping device has to be simple, easily installed, replaceable and effective.
The invention is particularly applicable to a sports racket which employs a network consisting of longitudinal strings and cross strings, the majority of longitudinal strings in the central portion of the string network, along the longitudinal axis of the racket, being directed in a fanout arrangement from the center of the network narrowing toward the handle, where at least a third of the longitudinal strings are anchored in the shank region between the throat and the handle. These longitudinal strings are preferably anchored at a single post in the shank region.
In the present invention, the affected longitudinal strings are wound around curved concentric openings formed in a string contact element of a string seating member attached to a string post which is secured to the racket frame. These concentric openings are approximately in the plane of or parallel to the string network while the string post is approximately perpendicular thereto. A shock absorbing material is positioned between the string post and the string contact element for damping the string vibration of the longitudinal strings entering and exiting the seating member set.
The present invention is an improvement of the invention disclosed and claimed in U.S. Pat. No. 4,988,101 to the inventor. In the patented device, the longitudinal strings being damped are wrapped around a string contact element wherein the wrapped portions of the strings are located in planes which are approximately normal to the plane of the string network rather than in a plane approximately parallel to the plane of the string network.